Crystal and Molecular Structure of Molybdenum Tetrachloride Oxide by Neutron and X-Ray Diffraction

Article abstract of DOI:10.1039/DT9800002006

The crystal and molecular structure of MoOCl4 has been determined by neutron and X-ray diffraction at 293 K and 77 K.A model, derived from consideration of the cubic close-packing together with an X-ray Patterson synthesis with Weissenberg data, was refined by the neutron powder profile-fitting technique to R = Σ0 - y_c>/Σy₀ = 0.094 (293 K) and 0.081 (77 K).The compound MoOCl4 is triclinic, space group PI, with unit-cell dimensions a = 6.255(4), b = 7.236(3), c = 7.134(3) Angstroem, α = 103.49(3), β = 107.02(6), and γ = 92.82(4) deg at 293 K.There are no large changes in the structure on cooling to 77 K.The Mo atoms occur in adjacent octahedral holes (Mo-Mo = 4.12 Angstroem) but there is no dimer formation as in MoCl5.The configuration around Mo is a square pyramid, with four basal chlorine atoms and an apical oxygen atom . The Mo atom is =0.41 Angstroem above the basal plane.There is longer Mo<...>Cl interaction of 2.9 Angstroem in the octahedral position through the basal plane; if this were stronger (ca.Angstroem), then the structure would consist of dimers.The structure is in agreement with a gas electron-diffraction study, which found a C_4v square pyramid with Mo-O = 1.658(5) and Mo-Cl = 2.279(3) Angstroem.It is also in agreement with the structures of WOCl4, ReOCl4, WSCl4, and WSBr4 where similar square pyramids are observed, but associated with different crystal symmetries.

Full text of DOI:10.1039/DT9800002006

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